Finding Meaning in Rodent Ultrasonic Vocalizations

Garet Lahvis, Oregon Health & Science University, USA

Many rodent species (Rodentia) emit vocalizations that communicate referential and emotional information. These vocalizations are emitted at frequencies that exceed human hearing abilities. With the advent of digital recordings of these ultrasonic vocalizations (USVs), there have been tremendous advances in our understanding of USV function. For instance, we now know that variations in predator threat elicit subtle differences in prairie dog alarm calls, which, in turn, engender predator-specific evasive behaviors. This model of referential communication (stimulus - vocalization - behavioral response) has also been employed to elucidate how emotional information is conveyed. For instance, rats and mice can learn that a tone predicts a stressful experience simply by hearing a companion rodent undergo this stressful contingency. These rodent studies have catalyzed new understanding of the neurobiological substrates of empathy. Rats also utilize different USV frequencies to indicate aggression versus affiliation. In turn, these USVs elicit different patterns of brain activity and behavioral responses of the rodents that hear these calls. These studies have opened new pathways to our understanding of rat psychological experience - what they prefer, what they find aversive. Mice also use different call patterns for different levels of social interaction. By integrating the use of spectrographic analyses with behavioral measures of classical and operant learning, we can begin to unravel the richness of rodent social experience and begin to explain the mechanisms of human social relationships, as never before possible.